From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
The specifications for an experimental 20 HP dynamo armature for larger output.
| Identifier | ExFiles\Box 68\4\ scan0248 | |
| Date | 28th March 1928 | |
| X5663 To BY.{R.W. Bailey - Chief Engineer} from EFC. c. BY/RD. EFC4/T28.3.28. 20 H.P. DYNAMO ARMATURE FOR LARGER OUTPUT WITH HIGHER CUTTING IN SPEED. Will you please have instructed experimental an armature for the 20 H.P. dynamo very similar but not quite the same as that asked for in our EFC3/T28.3.28 for the 40/50 H.P. case. This armature is to have 26 slots, 52 coils and commutator segments, and three turns per coil. The number of conductors will be 312 as in the other case, and these will be of 18 S.W.G. (.048") in place of 19 S.W.G. (.040") as at present standard. The number of conductors per slot will be 12 and working on the change of conductor dimensions with the same space for insulation as shown on your D.70974, it appears that the slot width and depth will be .166 x .487". There will be one lap coil incorporated in the winding in the same way that we at present incorporate the lap coil on our 28 slot armatures - 40/50 H.P. and 20 H.P. In this case, to some extent as an experiment, which we think will be found to be quite satisfactory, we are asking for a shorter step of coil viz. 5 (1 to 6) which introduces some amount of short chording. A rough diagram of the winding will be shown to Mr. Davis as a guide in making the diagram for the Expl. Shop. In this 20 H.P. case the special armature now asked for should be instructed to be suitable for the experimental 20 H.P. machine of the double brush type, of which we have had for some time three machines in this laboratory which will be available for this purpose. Contd. | ||